Congestive Heart Failure (CHF) can be caused by many different heart conditions in dogs and cats. It represents an advanced stage of heart disease. Mitral valve disease, DCM, ARVC and HCM are some of
the most common causes, but there are dozens of other possible diseases that may result in CHF.
CHF occurs when heart disease causes a decline in the pumping ability of the heart. Blood cannot move forward as it usually does, so it builds up behind the problem area (congestion). Pressure builds up in the blood vessels of the lungs if the left heart is failing, and in the blood vessels of the body cavities if the right heart is failing. When the pressure builds up high enough, fluid will leak out of the blood vessels. Fluid leaks into the lungs (pulmonary oedema) with left heart failure and into the abdomen or chest cavity with right heart failure.
In the lungs, this fluid fills the sacs where normally only air should be. The pet has to take more breaths to absorb the amount of oxygen they need. This increases the breathing rate and effort, which may be subtle at first, but can become quickly life-threatening.